Improvement in hygeometees



uiten tutes getint ffies.

as. vLAZELL, 0F WEST MERIDEN, coNNEcTIGT.'

`Letters P atent No. 75,432, dated Merch 10, i868.

.IMPROVEMENT IN HYGROMETERS.

En: Signalement tu it that ttters Extent mit mating-satt stille time. p

To ALL'wHoM IAT MAY c'oNoERN: i

Be it known that I, E. LAZELL, of West Meriden, inthe county `otNew Haven, and State of Connecticut, have invented certain new and useful Improvements in Hygremet'ers; and I do hereby declareA that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings,

makinga p'ertion of 'this specification, in which- Figure 1 is a plan view of a hygrometer constructed according to my invention. Figure 2 is an inverted plan view of the same. Similar letters ofv reference indicate correspondingv parts in both figures.

This invention consists in a semicircnlar wooden strip, formed with the grain of the wood transverse toits I length, and having one of its sides er surfaces coated with cement, or other material, in such manner as to exclude theairrtherefrom, so combined with a suitable index that the expansion or contraction of the strip i caused by the varying quantity of moisture absorbed by or evaporated from the expo'sed'suri'ace of the same,

will operate 1o turn the index' to indicate the deg-ree of humidityof the atmosphere. l

vTo enable others to understand the construction and operation of my invention, I will proceed to describe it with reference to the drawings.

A represents the circular case 'of the apparatus, and a shows the top plate fixed' in the upper part 0f the said case; any desired portion of the circumferential edge of this top plate having formed or marked upon it a scale, a*, which may be graduated in any suitable manner. Secured upon the upper end of the vertical central pivotpb is an index or finger, e, and secured to the lower end ofthe said pivot, underneath the top plate a, is a small pinion, d, which gears into a spur-wheel, e. Alconnectingrod,f, has one of its endsv pivoted upon a pin, b', attached to the spur-wheel e near the rim thereof, and its opposite end attached to the free extremity of a semicircular wooden strip, B, as shown at c', in iig. 2, the other or. opposite extremity of the saidrstrip being firmly attached to the side of the case A, as shown at 6*. This strip is formed with the groin of the wood lying in a position transverse to the length of the strip, and itsouter surface is coated, as indicated at c'twith cement, or with any other suitable material or substance, which will exclude air from the said surface, and thus render the same impervious to moisture. `Holes or openings, d*, are formed inthe sides of the case A, in order that the couditibncf the air within thesaidcase may be' the 'same as that of the atmosphere. Whenvthe humidity of the atmosphere increases, the exposed inner surface of the strip B'absorbs an additional quantity of mo'istnre .from the same, which causes the innermost side or portion of the said strip to expand, while no expansion takes place in the outermost side thereof, which is protected from moisture by the coating or covering edf-of cement,

or-other material, as hereinbefore set forth, so that by this means the'strip spreads or` expands to the arc of a larger circle, the free extremity thereof moving outward, and, acting through the rodjlspur-'wheelmjand pinion d, turns the index'to an extent proportioned to the increase of moisture in the air, and .thus causes the index to indicate suchjincrease upon the scale a*. When the humidity of the atmosphere is diminished, a'portion of i the moisture is abstracted or evaporated from the inner side of the strip 13,.. which .causes the said side to contract, and thus 'bring the strip tol the arc of a smaller circle, thus `moving the free extremity ofthe sadstrip inward aud'zpopcrating the indexto move in a reverse direction, and thus indicate the decrease of moisture in the air by its' changed position with reference to the graduations oi the scale. The strip B bcing constructed l l with the grain of Athe wood-situated transversely tothe length of the said strip, .thainner'or exposed surface thereof is 'rendered much more sensitive to the action of moisture than would -he the case if such grain were concentric with the arc. upon which .the strip is formed, and as a consequence the apparatus is rendered capable of indicating changes iu the degree of humidity of thc atmosphere with much greater niccty and exactitude than would otherwise be the case,

What I claim as my invention, and desire to secure by LcttersPatent, is.-

The curvilinear strip of weed, constructed as described, and having ont of its surfaces rendered impervious to-moistiire,`in combination with an index, substantially as and for the purpose specified. a. E. LAZELL. t

- Witnesses: A l

Guss. Peas, 'Wm CHAPMAN. 

